Frames of jaw crushers have been manufactured in many different ways. One typical frame of a jaw crusher comprises side plates and ends which are assembled with bolt joints. A jaw crusher may also comprise a completely casted or a completely welded frame.
Side plates of a jaw crusher are attached with bolt joints to, for example, casted ends in which shear forces created while loading the crusher are received with extending pins casted to the ends. The movement between friction surfaces of the bolt joints exposes joints to loosening and/or fretting fatigue that decreases considerably fatigue strength of the side plates and the ends. Due to the loosening frame bolts of the side plates attached to the ends require regular checking and when needed after-tightening.
Initiation of a crack from contact surfaces of two pieces pressed together is called fretting fatigue. For initiation of a crack typically a continuous low amplitude vibration gliding occurs between attaching surfaces of the side plates and the ends. Fretting fatigue is a very serious form of fatigue because it may also occur in such areas which are not critical regarding to stress. Controlling the fretting phenomenon is computationally difficult and laborious because influences of friction, such as friction coefficient, in joints are not accurately known.
Extending pins receiving shear forces of present multipart frame assembled with bolts and casted to the ends of the frame cannot be replaced when the pins wear away. In bolt joints, especially due to the large amount of frame bolts, lots of places critical to the fretting fatigue are caused to the frame because users easily forget after-tightening of frame bolts. Lots of frame bolts and massive base plates used with the frame bolts and lots of extending pins are used in the multipart frame of a jaw crusher due to which expensive machined surface must be plentifully produced to the frame. Thus, the amount of parts and expensive machining grows high that increases price and assembly time.
Very many critical fatigue vulnerable places are formed to a welded frame of a jaw crusher due to the high amount of welding seams, especially, if there are welding joints getting under stress in the area of the front wall subject to crushing load. Welding decreases fatigue strength of the base substance. Quality assurance of the weldings in the welded frame increases costs. Quality assurance in complex welded structures is difficult and expensive.
A thick intermediate piece behind a wear part of a fixed jaw is used to adjust the jaw angle of a jaw crusher in some applications, which intermediate piece may be replaced. The intermediate piece is heavy and difficult to mount. Relievings for decreasing weight have been made to the known adjustment plates of the jaw angle that increases manufacturing costs.
Patent publication EP1049539B1 describes a jaw crusher which has a frame assembled of many parts.